What focal length are you looking for? Are you shooting color or B&W? What's your budget? I (and I'm sure many here) have a collection of lenses surplus to my needs from old B&L RRs in kodak ball bearing shutters to the press camera standard 127 Ektar and 135 Optar, to modern plasmats. With a little care, you'd be amazed at the quality of the image from a $20 RR. If you don't need a lot of movements, both the Ektar and Optar are fine coated lenses in the $50-75 range.

Dan